1. Field of the Invention
The present invention relates generally to balancing machines and more particularly to a balancing machine for balancing vehicle wheels and indicating the position and weight required for balancing the wheel.
2. Background of the Prior Art
Prior art wheel balancers have generally been of two types: static or one plane balancers and dynamic or two plane balancers. In a static wheel balancer, the wheel is removed from the vehicle and is placed on a stand with the wheel generally defining a horizontal plane and the rotation axis of the wheel being disposed vertically and perpendicular to the plane. The stand permits the wheel to float and assume a stable position. A level bubble is associated with the wheel to be balanced and gives an indication of direction and degree of tilt of the rotation axis of the wheel. Weights are added until the rotation axis is truly vertical.
In a dynamic wheel balancer, the wheel is rotated either on the vehicle on which it is mounted or removed from the vehicle and mounted on a drive shaft of a wheel balancing machine and rotated. When the shaft and wheel are rotated, the out of balance forces cause the drive shaft to vibrate. The operator applies weights until the drive shaft remains on axis as the wheel is rotated.
In one type of dynamic balancer, a rotatable shaft receives an imbalanced wheel. The rotatable shaft is supported at several points where vibration transducers are fitted so that the imbalance is detected and compensated in two planes.
With conventional balancing devices, electric signals are produced by means of transducers which detect vibrations and produce electrical signals. These signals are used to determine the size and angular position of imbalance in both compensation planes, which, in the case of motor vehicle wheels, lie at the inside and outside of the rim. By applying the compensating weights at the determined points of the rim, i.e., in the corresponding planes of the imbalanced rotor, imbalances can be compensated statically and dynamically.
During dynamic balancing of imbalanced rotors, the latter are brought in rotation with the shaft carrying the imbalanced rotor, e.g., the motor vehicle wheel, supported in two planes. Basically, there are several ways to balance, which depend on the relation between the natural frequency of the rotor to be balanced and its suspension and the rotational speed of the imbalanced rotor to be tested.
Although the prior art devices provide generally reliable readings of weights and their positions, there is a price to be paid between accuracy and machine cost. Typically, the most accurate wheel balancers are relatively expensive. Thus, there is a need for a wheel balancing machine of the electronic type which provides highly accurate readings of the position and weight required for balancing a rotor, such as a vehicle wheel, the machine being of reduced cost. The present invention is directed toward filling that need.